|Simplified Chinese (China)||照妖镜
|照 zhào =
'to reflect, show, look into (mirror)'.
妖 yāo = 'ghost, demon, monster'.
镜 jìng = 'mirror'.
|Traditional Chinese (Taiwan)||仇敵鏡
|仇敵 chóudí =
鏡 jìng = 'mirror'.
|敵 teki =
鏡 kagami = 'mirror'.
Gương Chiếu Thù
|Gương = 'mirror'.
Thù (仇) = 'enemy'.
Gương = 'mirror'.
Chiếu (照) = 'to light up, project, show'.
Thù (仇) = 'enemy'
Show enemy mirror
The Foe-Glass is a 'Dark detector', a mirror that tells you when your enemies are close by. The imposter Mad-Eye Moody had one (Book 4, Chapter 20) but it proved to be of little use in the end because he forgot to look into it. The same Foe-Glass turned up again in the Room of Requirement (Book 5 Chapter 18). For more information, see Harry Potter Lexicon: Magical Items and Devices).
'Foe-Glass' sounds a little old-fashioned in English. In modern terms it might be called an 'Enemy Mirror'. That is how it is treated by the Japanese, Taiwanese, and Vietnamese translators (the Vietnamese translator uses different terms at different places). The Taiwanese translator uses a somewhat formal term for 'enemy' or 'foe'.
The most interesting is the Mainland version, which translates it as 照妖镜 zhàoyāo-jìng. This is a type of magic mirror from Chinese tradition that shows a monster for what it really is. (照妖镜 zhàoyāo-jìng is also used more broadly in modern Chinese for anything that will distinguish between the real and the fake, or anything that will show someone's true colours). However, Moody's demon-revealing mirror failed to show that Moody himself was an imposter!